The present invention relates to a method of measuring damage to grain; and more particularly, it is directed to measuring the mechanical damage to grain kernels, such as corn, which occurs during harvesting, drying and handling. Although the disclosure deals specifically with corn, persons skilled in the art will readily appreciate that the method of the present invention may be applied to other grain kernels having internal protein, all of which are subject to mechanical damage during harvesting, drying and handling.
Standing in the fields, unhusked corn is undamaged and can last almost indefinitely when direct without diminishing its food value for man and animals. Deterioration begins with the mechanical process of harvesting, and practically every subsequent operation in the drying, transporting and handling further decreases the quality of the grain. The rate of deterioration is dependent on the initial injury sustained during such mechanical processes, particularly the harvesting operation. During harvesting, the corn kernels are subjected to damaging impact and compressive forces which result in breaches or cracks in the pericarp of the kernels. Mold will grow in the cracks or interstices of the corn kernels to such an extent that an entire shipment may be destroyed. Government guidelines have been established, for example, in the amount of Aflatoxin that may be found in grains. If the guidelines are exceeded, the shipment may be seized by the Food and Drug Administration. In all probability, the regulations regarding toxins in feed corn will become more stringent in the future.
Because practically no measurements are currently made concerning the concentration of toxins at the initial selling point, and no discounts applied for mechanical damage, there is little or no incentive for the actual producer of the crop to minimize mechanical damage. Further, there is no commercial apparatus or method available for measuring mechanical damage to corn as it is being harvested. If such a method were available, farmers could adjust their combines to minimize the mechanical damage which would result in great savings which could be passed on to consumers.
A number of indices or tests have been proposed for measuring mechanical damage, but these have been primarily of theoretical or academic interest. It is believed that much of the waste due to mechanical damage could be reduced or eliminated if, for example, grain elevators or markets could establish a purchase price based, at least in part, on discounts for the mechanical damage of the corn as it is delivered. This would add some incentive to the farmer to properly adjust his combine.
As indicated above, systems have been proposed for measuring mechanical damage to corn, but none of these systems have had any degree of universal acceptance.
Photoelectric quality control devices have been used to sort agricultural products for many years. For example, it was suggested that stained damaged seed be removed with commercially available color sorting equipment. The principal disadvantages of such commercial units is the high initial cost, low capacity, and need for specially trained operators.
Other workers have utilized a device to facilitate optical sorting of middle rice based on translucence differences. Seventy-five percent of the damaged kernels were removed based on differences of transmittance of individual kernels. One researcher reported that available color sorters were not suitable in evaluating corn damage.
Research workers have utilized fast green dye to facilitate visual inspection for mechanical damage or corn samples. A commercial sorter was developed and used to sort products tainted with Aflatoxin from consumable food products. This machine uses an ultraviolet light which activates a fluorescent material produced by Aspergillis Flavus and a photodetector to distinguish between contaminated material and the product that contains no toxins.
The use of fluorescent pigments has found wide acceptance and utility in many areas of research and commercial application in the agricultural field. Fluorescent materials have the property that, when stimulated by a suitable light source, they emit light of a longer wavelength than the incident light. In practice, ultraviolet light is used as the source, and the emission is in the visible spectrum.
In the present invention, corn kernels are treated with a reacting solution containing an agent that selectively reacts with the damaged portions of the kernels--specifically, the agent forms a fluorescent bond when it comes in contact with the kernel protein which is exposed when the outer shell of the kernel is breached. The agent may conveniently be applied in aqueous solution. The kernels are washed after application of the agent to remove the excess agent, and they are dried for convenience in handling. The treated corn is then ground to a fine powder. The exposed surface of the corn protein bonds to the agent so that after grinding, the products of the reaction which contain the agent are representative of the cumulative area of the interior of the corn exposed through breach. The powder is then spread into a uniform field and exposed to an ultraviolet light source, and the resulting fluorescent light is measured. Thus, the volumetric damaged surface is converted to an area measurement. The fluorometer response is a linear function of the area of fluorescing material. The measurement of the fluorometer is therefore proportional to the original three-dimensional area exposed through mechanical damage.
By grinding the corn prior to illuminating it to cause fluorescence, we have eliminated any dependence of the measurement system on the orientation of the corn kernels. Further, damage is measured as a function of the exposed surface. If the whole kernels were used for measurement, the shape and depth of the damage breach would have an effect on the measurement. For example, a deep, narrow cut may emit a relatively smaller amount of detectable fluorescence, whereas a shallow surface breach may expose less total area of endosperm, but result in a larger detected fluorescence. The present invention also obviates the problem of different readings due to the location of kernels relative to the transducer-sensing fluorescence, as will be clear from the detailed description below.
The present method is reliable and repeatable, and it does not take a long time to perform the test, usually less than about 5 minutes. The method may be practiced on all varieties of corn, and it is independent of the original moisture content of the sample. The present method is also inexpensive (because it is applied to and destroys only a small sample of the crops and the equipment and materials are relatively inexpensive). Further, it is simple and reliable enough to be performed by relatively unskilled labor.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.